The project is a component of a NIDA-funded Center for Prevention Research at the University of Kentucky. The purpose of the studies described in this project is to compare the behavioral effects and abuse liability of d-amphetamine (AMPH) in young adults who are high-or low-sensation seekers, based on rigorous assessment criteria. High (HSS) and low- sensation seekers (LSS) will be selected from a population of young adults in the Lexington area who remained in the upper and lower thirds of thier age-matched cohorts.